Symbol 
Definition 
Units 
MC 
Moisture content. Mass of liquid in sludge /
mass of sludge 
% 
SC 
Solids content. Mass of solids ( dry mass )
in sludge / mass of sludge

% 
V 
Volume of sludge or filtrate 
m^{ 3 } 
M_{ S } 
Mass of dry solids in sludge 
kg 
M_{ W } 
Mass of liquid in sludge 
kg 
VM 
Volatile matter ( = organic content ) 
% 
TS 
Total solids 
kg 
X 
Volume of digester gas used in boiler 
m^{ 3 } 
r 
Specific resistance to dewaterability 
m / kg 
C 
Solids concentrations in sludge 
kg / m^{ 3 } 
THETA 
Filtration time 
s 
MU 
Absolute viscosity of filtrate 
N . s / m^{ 2 } 
P 
Pressure ( difference ) across filter 
N / m^{ 2 } 
A 
Filter area 
m^{ 2 } 
R_{ M } 
Resistance of filter paper, cloth or septum 
1 / m 
b 
Slope of THETA / V versus V plot 
s / m^{ 6 } 
r_{ O } 
Specific resistance constant 
 
S 
Coefficient of compressibility 
Dimensionless 
C_{ T } 
Mass of solids / unit volume of liquid
in the sludge 
kg / m^{ 3 } 
Y 
Yield of vacuum filter 
kg / m^{ 2 } . s 
A_{ F } 
Area of cake formation as fraction of
total area 
 
THETA_{R} 
Time of l revolution 
s 
f_{ E } 
Cake correction factor, ratio mass of
liquid / unit mass sludge : mass of filtrate / unit mass sludge dewatered 
 
SC ( Sl ) 
Solids content of wet sludge 
Fraction 
SC ( C ) 
Solids content of sludge as it
emerges from the filter bath 
Fraction 
T 
Time of pressure filtration 
h 
k 
Constant of proportionality, emprical 
kg^{ 2 } / m^{ 2 } . s for
T in s 
SC ( F ) 
Final cake solids content at end of
filter pressing 
Fraction 
H 
Heat energy required to raise water to
incinerator exit temperature 
J 
T_{ L } 
Inlet temperature of sludge 
^{ O }C 
T_{ E } 
Exit temperature of exhaust gases 
^{ O }C 
K 
Calorific value or energy / volume of
combustible material 
J / kg 
CM 
Combustible material ( almost equivalent
to organic material ) 
 
Z 
Fraction of calorific value taken up by
incinerator heat loss 
 